1. Field of the Invention
This invention relates to a knife used in a wood chipper such as a rotatable disc type with a plurality of circumferentially spaced chip openings through the disc.
2. Prior Art
Wood chippers having rotatable cutters, or drums, or rotatable chipping discs with openings through which chips may pass, and fitted with double-edged knives are known in the art.
A single reshaping of the knife blade, involving the removal of material from one or both of the edge surfaces forming the cutting edges of a double-edged knife (known in the art as counter grinding), is often the only reshaping or resharpening of a knife blade before it is discarded.
One aspect of the geometry of knives is that knives having a large wedge angle, i.e., the angle between the two surfaces converging to the cutting edge, remain sharper longer and therefore are more popular. However, the larger wedge angles are more likely to cut a chip by shearing the chip from the incoming material rather than by cleavage. More force is required to sever chips by shearing than by cleavage, and thus more power is required for operation of a disc chipper having knives with larger wedge angles.
Another problem is the penetration of chip particles between the knife and the knife holding means beneath the knife, typically a counter knife, that can cause excessive pressure on the knife which may bend it.